April 9, 2020

Skating rinks on Ceres? Ice could be source of bright spots


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This animation shows a sequence of images taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 kilometers), in its RC3 mapping orbit. The image resolution is 0.8 mile (1.3 kilometers) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Scientists studying fresh pictures from NASA’s Dawn mission say gleaming dots seen on the dwarf planet Ceres may be from icy patches reflecting sunlight back into space.

The bright spots caught the attention of Dawn’s science team as the solar-powered probe approached Ceres early this year, fueling speculation the dots at the bottom of a crater could be from ice volcanoes or frozen material exposed by a violent impact with another object.

Experts now believe the features come from something on the dwarf planet’s surface and are not evidence for cryovolcanoes.

“Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice,” said Christopher Russell, Dawn’s principal investigator at UCLA.

Dawn’s framing camera recorded the latest images of the bright spots on May 3 and 4 from a distance of 8,400 miles.

“In this closest-yet view, the brightest spots within a crater in the northern hemisphere are revealed to be composed of many smaller spots. However, their exact nature remains unknown,” said a press release issued by NASA’s Jet Propulsion Laboratory.

Dawn was captured by the gravity of Ceres on March 6 and looped into the first of a series of science orbits April 23, completing a 15-day lap around the dwarf planet at a distance of 8,400 miles.

The spacecraft re-activated its ion propulsion system Saturday to spiral closer to Ceres, driving toward a June 6 arrival in a 2,700-mile-high orbit. Officials say Dawn will pause twice during the transfer into the new orbit to take images of Ceres.

Ceres is the largest object in the asteroid belt between the orbits of Mars and Jupiter. The icy world measures nearly 600 miles across and was unexplored before Dawn’s mission.

The Dawn probe visited asteroid Vesta in 2011 and 2012, then journeyed across the solar system to Ceres, an achievement made possible by the craft’s three xenon-fueled thrusters, which operate more efficiently than conventional liquid-fueled propulsion.

Mission managers expect Dawn to study Ceres until at least mid-2016, approaching as close as 232 miles from the body’s surface to obtain higher-resolution images, detailed composition maps and an assessment of its gravity field.

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Follow Stephen Clark on Twitter: @StephenClark1.


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